Oil conversion



Patented Jan. 16, 1934 YFEC E yoIL CONVERSION Albert G. PeterkimJr.,Bryn Mawr, Pa., assigner. to The Atlantic Refining Company,Philadelphia, Pa., a corporation of Pennsylvania` Application May 14,1929. Serial No. 363,023

. 1 claim. (ol. 19e-4s) My invention relates to conversion or crack ingof hydrocarbon oils, particularly petroleum or components thereof ofhigh boiling point, to produce lower boiling oils, such as gasoline,which 5 are suitable for use as motor fuels in internal combustionengines; more particularly my invention relates to the cracking of oilsof high specie gravity, such as residual oil resulting from cracking ornon-cracking distillation.

In :accordance with my invention, oilsY of such high boiling point, highspecic gravity and objectionable solid content or other properties whichrender them dinicult and relatively costly` to treat by usual crackingprocesses, are converted or cracked with relative ease and atcomparativelylow cost to form solid coke, suitable for use as fuel,lower boiling oil suitable for use asrmotor fuel or for further crackingto produce motor fuel, and gas which may be used as fuel or in themanufacture of salable Vproducts, as, for example, higher alcohols orthe like. Y A distinct advantage of my invention is a highly eiilcientheat interchange between the charging stock introduced into the systemand the vapors evolved therein, thus necessitating the application of aminimum amount of heat from an external source to raise the chargingstock to the desired temperature. I

My invention relates to improvements in cracking processes wherebyhydrocarbon oils, particularly heavy oils, as for example, of a gravityof from about 10 to about20 A. P. I., which may be obtained fromdistillation or crude petroleum, or which may be residual oil from acracking operation, or a heavy crude petroleum, can be economicallycracked without dilution and without substantial carbon deposition onthe still walls, thereby eliminating the necessity of frequent cleaning,and reducing deterioration of the still.

More particularly in accordance with my invention, a heavy oil, or amixture of ltwo or more heavy oils, of the type aforesaid, which haspreviously been heated to a suitable temperature below that of incipientcracking, is introduced into a chamber, preferably not externallyheated, and simultaneously there is introduced into the chamber to raisethe heavy oil to cracking temperature, a highly heated oil, preferablyreaction products from a cracking operation. Thus heat is applied to theheavy oil in the chamber by means of the highly heated y oil, andsubstantial cracking of the heavy oil is effected, with the formation ofvolatile products, which may be conducted from the chamber as fluid, andcoke, which deposits in the chamber, this without need to subject theheavy oil to an externally heated surface.

Further in accordanceV with my invention, the volatile productsresulting from the cracking of the heavy oil in the manner abovedescribed are conducted to suitable dephlegmating or fractionatingapparatus wherein Va liquid fraction whose properties areunsuitable toadapt it for use as motor fuel is separated. This fraction is passedfrom the dephlegmator or fractionator into cracking apparatus and theproducts resultingv from the treatment effected in such apparatus areintroduced into the chamber aforesaid. By so operating, substantialcracking of the fraction occurs whereupon there are producedhydrocarbons of still lower boiling point, and the products as a wholein their highly heated condition are used to crack the heavy oil.

Generically, the method and apparatus of my present invention are thoseof my prior application Serial No. 320,778, led November 2l, 1928. Mypresent invention is` differentiated from my invention of my aforesaidapplication however, particularly in that the heavy oil, beforeintroduction into the cracking or coking chamber, is preheated to'alower temperature, to wit, to a temperature below thatV of incipientcracking. My present invention departs further from that of my aforesaidprior application in various respects, hereinafter appearing, such aspreheating of the heavy oil in one or more heat exchangers prior tointroduction into the cracking or coking chamber, either directly fromthe preheating system aforesaid,`or through a heating furnace, whichVlatter however, as to' some aspects of my invention, may be omitted.

Referring to the drawing, 1 is a pipe equipped with pump 2 which leadsto the inlet end of coil 3 arranged in the upper portion of thefractionating column C. From the outlet end of coil 3 the line 4 leadsto the coil or tubes 5 of heat exchanger H, from which line 7 controlledby valve 7a leads to the tubes 9 ofifurnace'A, fired vby burner a t0which' is supplied fuel, as gas. connects line 8 controlledby valve 8aleading to the lower portion of the chamber B. With line 8 connects theline'la equipped with pump 2a and control valve 1b through which freshcharging stock, as for example, gas oil, may be fed into said line,thence into chamber B.

With the outlet of tubes 9 is connected line 10 which leads into thelower part of chamber B, preferably heat insulated bymeans of insulatingmaterial i; however', it shall be understood that this' insulation isfor Vheat economy and is not indispensable.

with the une 7 J There connects with thev upper part of chamber B a line11 controlled by valve 11a which communicates with the lower part ofheat exchanger H with the upper part ofY which there connects line 12through which vapors from chamber B are passed from exchanger H to thelower portion of the fractionating column C. Trapped line 13 controlledby valve 13a connects the lower part of heat exchanger H with the lowerpart of fractionating column C. Line 14 controlled by valve 140.connects line 13 with pipe 15, which connects the lower part of thefractionating column C through pump 16 with the inlet end of tubes 17lof the furnace D, fired with gas or other suitable fuel delivered to theburner d.

From the outlet of the tubes 17 line 18 controlled by valve 18a extendsinto and downwardly in chamber B, discharging into its lower portion.

The fractionating column C may be of any suitable type; the oneillustrated having fractionating plates b equipped with downiiow pipes eand vapor uptakes f with bubbler caps g. Line 19 connects the upperportion of the columnY with partial condenser E, in turn connected byline 19a to reflux proportioning device R. having leading therefromtrapped line 19d controlled by valve 19e leading to the upper portion ofthe column C, and line 195 controlled by valve 19e leading to the inletof coil 20 in condenser K. From the outlet of the coil 20 line 21 leadsto gas separator F, having lines 22 and 23, controlled by valves 22a and23a, respectively, which serve respectively to conduct gas and liquidfrom the system.

Adjacent the bottom of the chamber B may be provided a pipe 24,controlled by valve 25, for drawing off condensate or liquid oil duringthe starting period.

In carrying out my process in apparatus of the type described, heavyoil, as, for example, bottoms from the non-cracking distillation of Mid-Continent crude petroleum, having a gravity of 12 A. P. I., is fed bymeans of pump 2 through pipe 1 through the coil 3, line 4 and coil 5. Inpassing through the coil 3 the temperature of the oil is raised byvapors passing upwardly through the fractionating column C, ashereinafter described; and in passing through coil 5, in which it isbrought into heat interchange relation with vapors passing upwardlythrough the heat exchanger H, as hereinafter described, the temperatureof the oil is further raised.

After passing through coil 5 the heated oil is conducted through line 7into tubes 9 of the furnace A where it is raised to the desiredtemperature. However, if desired, by regulating valves 7a and 8a, inlines 7 and 8, respectively, a portion of the oil leaving coil 5 may bepassed directly into chamber B, or all of the oil from coil 5 may bepassed directly into said chamber through line 8.

Unheated oil, of any suitable character, generally fresh feed oil, maybe introduced directly into the chamber B through lines la and 8, eitheralone or in mixture with preheated oil, depending upon the setting ofvalve 8a. In either case the valve 7a may be open or closed, permittingor preventing oil to pass at the same time through the heater tubes 9into chamber B.

rI'he temperature toy which the oil is-raised before it is introducedinto the coking chamber B will depend upon the temperature of the highlyheated products introduced into chamber B from tubes 17, upon therelative proportions of those highly heated products to heavy oil, andupon the nature of the particular heavy oil introduced into the systemthrough pipe 1 and/ or pipe 1a. Such temperature is so regulated as toeffect substan- 'tial cracking of the heavy oil while in the chamber B,in which obtains any suitable pressure, as, for example 30 pounds persquare inch gauge, thereby to form lower boiling hydrocarbon oils, gasand solid coke. It is possible that it may be ature that substantialcracking thereof will occur before it isv introduced into the chamber B.Under such conditions the velocity of the heavy oil through the tubes 9of the furnace A is so lcontrolled that carbon deposition in the tubes 9does not occur.

.Vapors of products introduced into and/or formed in the chamber B arepassed along with the uncondensed gases formed through line 11 into heatexchanger H where they are brought into heat exchange relation with theresidual oil passing through coil 5. From the upper portion of the heatexchanger H the vapors are conducted through the line 12 into the lowerportion of the fractionating column C. The vapors and gases passupwardly through the fractionating column countercurrent to and incontact with reflux liquid which passes downwardly from plate to platetherein; the vapors are fractionated and separated into fractions ofvarious boiling ranges. The vapors which reach the portion of thefractionating column in which the coil 3 is located are partiallycondensed by heat exchange which takes place between them and the oilpassing through that coil, and the condensate passes downwardly throughthe column to serve as reflux liquid. The vapors and gases uncondensedby-contact with the coil- 3 leave the column C through line 19 and passinto the partial condenser E where a portion of the vapors is condensed,and the condensate is passed through line 19a into reflux proportioningdevice R which may be adjusted to return to the column any desiredproportion of the condensate as reflux, so that in case insufficientreliux is supplied by condensation of the vapors effected by coil 3,suflicient additional reiiux may be supplied from the device R. Thatportion of the condensate which is not returned to the column C and theremaining uncondensed vapors pass through line 19h into the condenser Kwhere the remaining vapors are liquefied. The condensate and uncondensedgases then pass through line 2l into gas separator F where separation ofthe uncondensed gases from the liquid is effected. The uncondensed gasespass from the separator through line 22 to suitable gas storage (notshown), while the liquid is withdrawn through line 23 and passed tosuitable liquid storage (not shown).

That portion of the vapors which condenses portion of such liquid may bepassed through line 14 directly into line l5 which leads from the lowerpart of the fractionating column. There is conducted through line 15 theliquid which collects in the lower part of the fractionating column, andby means of the' pump 16 this liquid and the liquid passed into the line15 through line 14, constituting an oil of intermediate boiling point,such as gas oil, are pumped into the tubes 17 of the furnace D where theoil is maintained under such temperature and pressure as will causecracking of the oil passed through tubes 17. For example, in the tubes17 the oil attains a temperature from about 750o F. to upwards of' l000F., and the pressure upon the oil in tubes 17 is determined by pump! 16and setting of valve 18a, and may vary from atmospheric pressuretoupwards of 1000 pounds per square inch gauge.

The highly heated products from the tubes 17 are conducted `through line18 into the lower pornecessary to raise the heavy oil to such tempertionof the chamber B, their pressure being suitido lio

ably reduced as they pass through valve 18a. In chamber B the highlyheated products are brought into contact and heat exchange relation withthe preheated heavy oil which has been introduced intothat chamberthrough line 10 and/or line 8. This causes substantial cracking of theheavy oil in the chamber B, tol form a lower boiling oil and gas, whichpass in the iluid state from the chamber through line 11, and coke whichdeposits in the chamber and is from time toi time removed therefrom.

There is passed from chamber B through line 11 into heat exchanger I-I amixture of the volatile portion of the cracked products, introduced fromtubes 17 into the chamber B, which portion comprises low boiling oilssuitable for use as motor fuel and oils unsuitable for such use butwhich are suitable for recracking, with the volatile products, resultingfrom the cracking of the heavy oil in chamber B, which latter oil maycomprise to a relatively large extent vapors of an oil suitable forcracking at high temperatures. In heat exchanger H the heavier portionof the oil is condensed due to loss of heat to the cooling medium, whichmay be charging stock as described, passing through the coil 5. Theuncondensed portion of the vapors passes from the upper part ofexchanger H through the line 12 into the lower part of the iractionatingcolumn C and upwardly therethrough countercurrent to and in contact withdescending reflux liquid, as

heretofore stated.

The drawing is a diagrammatic illustration of one form of my apparatusand is for the purpose of explaining my invention. Details, such asopenings to permit removal of coke, and other structural modiiicationsor features which are well known to those skilled in the art, are notshown. As an example of a modiiication, in lieu 0I the separate heatexchanger H. the coil 5 may be disposed in the lower part of thefractionating column C.

Moreover, while only one coking chamber B is shown, it shall beunderstood that a second coking chamber may be installed, and usedduring the removal of coke from the first.

It shall be further understood that the portion of my apparatus, astubes 17, wherein cracking is eiected, is illustrated generically, andthat any suitable system or apparatus for cracking oil, from whichreaction products may be introduced into the coking chamber B, may beused. My invention is therefore not limited to the particular modedescribed for cracking the high W boiling distillates recovered from thefractionating column. For example, the cracked products from the tubes17 may be passed through intermediate apparatus for further treatment ofany kind, including cracking, before passing to the chamber B. Or thepressure reducing valve 18a may be omitted and the oil in tubes 17maintained under the pressure existing in the coking chamber B, in whichby regulating valve 11a may be maintained any suitable pressure.

Temperature conditions in the diierent parts of the system may vary. Ingeneral, however, it is preferable to heat the heavy oil beforeintroduction into the chamber B to a temperature below that of incipientcracking, but preferably at least to @6 F. When the furnace A isutilized as part of the preheating system (it being understood that thefurnace A may be omitted and preheated oil introduced into the chamber Blcoke or carbonaceous material within those tubes.

However, utilization of the preheaters, as exchanger H and/or coil 3, isof advantage even in those cases where the oil attains in the tubes 9 atemperature at which more or less cracking occurs.

The temperature attained by the oil in the coil 17 is preferably inexcess of 800 F. to elTect considerable cracking. In general, however,the cracking system or zone generically represented by the coil 17 maybe operated under any suitable conditions, as to temperature andpressure, and generally such as are commonly utilized in the cracking ofgas oil or the like.

It will be apparent from the foregoing that my invention contemplatestwo cooperative cracking systems, one of which includes a cracking zone,such as the chamber B, in which substantially all of the cracking ofheavy oil is effected, such oil preferably having previously beenpreheated and maintained at or raised to its cracking temperature,whereby coke, lower boiling oils and gas are formed, by introductionthereinto of reaction products from the other or second cracking zone inwhich is cracked a lower boiling oil, derived either from a separatesource or from the iirst cracking zone, or comprising a mixture of oilfrom a separate source with'oil derived from the first cracking zone.

For brevity in the appended claim the term heavy oil refers to oiloperated upon in the j first oil heating or cracking system and includesheavy oils of the character herein dened by that term; the termintermediate boiling point is employed generically to designate the oillighter than said heavy oil, charged into the second cracking system;and the term low boiling point is employed generically to designate oilconstituting an ultimate product, such as cracked naphtha, gasoline orother oil of boiling point lower than that of the oil charged into thecracking and coking system.

What I claim is:

A combined cracking and coking process for converting hydrocarbon oilinto a light distillate and coke as final products that comprisesretaining hydrocarbons maintained at coking temperature in a cokingchamber to convert the same to a coke residue, subjecting the evolvedvapors to fractionation to form a vapor fraction and a refluxcondensate, condensing said vapor fractemperature into the cokingchamber, separately heating a stream of charging stock comprising apetroleum residuum to between 400 F. and a temperature at whichsubstantial amounts of carbon would be deposited from the residuum asthe heating proceeds by subjecting said residuum to indirect heatexchange with uncooled vapors leaving said coking chamber, and directingthe heated stream into the coking chamber, and introducing an unheatedgas-oil charging stock into the heated stream of petroleum residuum *lentering the coking chamber.

ALBERT G. PETERKIN, JR.

